1. Field of the Invention
The present invention relates to a scroll type fluid machine to be used as a compressor or an expander, particularly, relates to a mechanism preventing rotation of a swiveling scroll.
This application is based on Japanese Patent Application Nos. Hei 10-350262 and Hei 11-203922 the contents of which are incorporated herein by reference.
2. Discussion of the Background
A mechanism preventing rotation of a swiveling scroll, for example, as shown in Japanese Unexamined Patent Application, First Publication, Nos. Sho 58-20401 (Kokai) and Sho 59-68585 (Kokai), having a swiveling scroll 1 comprising an end plate 1a and a swivel pin 1b provided projectingly from the end plate 1a, a housing 2 comprising a housing pin 2a provided projectingly from the housing 2, and a pin engaging member 3 through which the swivel pin 1b and the housing pin 2a are connected (see FIGS. 10 and 11), is known.
In the pin engaging member 3, two holes 4 are formed at a distance of e and the swivel pin 1b and the housing pin 2a are inserted into the holes 4 respectively in order to form the mechanism preventing rotation. In this mechanism preventing rotation, a crank 5 having an eccentricity distance .rho. which is the same as the distance e is combined with a bearing 6 at the side of the swiveling scroll 1, then, a quadric link L as shown in FIG. 11 is formed, so that only rotation is prevented without preventing its revolution in the swiveling scroll 1.
The mechanism preventing rotation makes it possible to decrease a number of components and thus simplify the mechanism in comparison with a mechanism preventing rotation with a conventional Oldham ring or ball coupling, so that the mechanism preventing rotation can have advantages of miniaturization and lightening of the mechanism. Furthermore, the pin engaging member 3 and the like composing the mechanism preventing rotation can be easily prepared, therefore, cost can be reduced.
In the mechanism preventing rotation, since a relative distance between the swivel pin 1b and the housing pin 2a maintains the constant value (=e), a swivel diameter of the swiveling scroll 1 also keeps a constant value. Accordingly, if there is an engaging position error in the engagement of the swiveling scroll 1 and a stationary scroll (not shown), a gap occurs by the position error and liquid leaks through the gap, so that a volumetric efficiency may decrease or disperse.
On the other hand, a mechanism preventing rotation having a ring-shape pin engaging member 7 of which a swivel pin 1b and a housing pin 2a are inserted into an inner space portion 7a, as shown a principal portion thereof in FIGS. 12 and 13, is disclosed in Japanese Examined Patent Application, Second Publication, No. 6-68276 (Kokoku).
In this composition, variation of the relative distance between the swivel pin 1b and the housing pin 2a is accepted, so that the swivel diameter of the swiveling scroll 1 is variable and the engaging position error in the engagement between both scrolls can be offset.
However, the mechanism preventing rotation has the pin engaging member 7 which rolls according to the revolutional swivel movement of the swiveling scroll 1 and the swivel pin 1b and the housing pin 2a rolling-contact with the inside surface of the pin engaging member 7, and therefore, this mechanism preventing rotation has the disadvantage that each of these pins 1b and 2a, and the pin engaging member 7 has short fatigue life.
Moreover, by reason of design, when the pin diameters of the swivel pin 1b and the housing pin 2a are changed, a difference occurs among each relative rolling velocity of the pin 1b, 2a, and the pin engaging member 7 in the rolling contact, and accordingly, a relative slip occurs between one pin 1b (or 2a) and the pin engaging member 7, and thus partial wearing may occur. Therefore, there is a disadvantage that it is difficult to respond to design changes.